Various devices and methods have been traditionally used to combat a physical condition known as Barrett's esophagus. Barrett's esophagus is the abnormal growth of intestinal type cells into the esophagus as a result of stomach acid chronically refluxing into the esophagus. Most people occasionally experience heartburn, which is the refluxing of stomach acid beyond the lower esophageal sphincter muscle and into the esophagus, and is not harmful. Severe or frequent reflux, however, is harmful and known by the names gastroesophageal reflux disease (GERD) and chronic reflux esophagitis (also known as Chronic Acid Reflux, or CAR). About one out of every ten patients with GERD/CAR are found to have a condition known as Barrett's esophagus. In patients with Barrett's esophagus, the healthy mucosal cells of the inner layer, or the squamous epithelium, of the esophagus are replaced with diseased, or intestinal cells. It is believed that such growth is a defense mechanism of the body to avoid esophageal injury due to the acid refluxed from the stomach. Unfortunately, these mucosal tissue changes may lead to low, then high grade dysplasia, and eventually to cancer of the lower esophagus, known as adenocarcinoma.
A common method for destroying diseased esophageal tissue has been to cauterize the unwanted tissue with a conventional ablation device. Ablation devices have developed as an alternative to other traditional means for eliminating unwanted tissue, such as by cutting away the tissue, cryotherapy, and thermal therapy. Cryotherapy is the application of extreme cold to freeze and destroy diseased mucosal tissue. Thermal therapy is the application of heat to burn diseased mucosal tissue. In use, these devices are placed next to or in contact with the unwanted tissue and tissue is ablated, cauterized, coagulated, frozen, or burnt, as the case may be, by energy transmitted from or to the device.
Traditional ablation devices have two primary shortcomings. First, traditional devices ablate only relatively small portions of patient tissue at one time. The energy transmitting elements of these conventional devices usually cover a portion of the outer surface of the device. Thus, the area ablated in a single energy transmission is substantially equal to the surface area covered by the energy transmitting elements. The area ablated in a single energy transmission with conventional devices is generally limited to a width of about 3 millimeters and a length of between 5 millimeters and 15 millimeters.
A second primary shortcoming of traditional ablation devices is their inaccuracy in use. A main challenge for battling Barrett's esophagus is to destroy targeted tissue without affecting healthy adjacent esophageal cells or muscular cells underlying the diseased tissue. Injury to the healthy underlying muscular tissue, for example, can lead to the creation of a stricture or constriction in the esophagus. Many conventional ablation devices have opaque probes for ablating tissue. The probes contain the energy transferring elements with which the unwanted tissue is destroyed. The inability to view through the probe leads to maneuvering difficulties and reduced accuracy in use. For instance, because the probe is not visually transparent, a user must estimate the position of the energy transferring elements when positioning of the device within the patient and during the energy transmitting procedure. The requirement to estimate the position of the elements during the energy transmission prevents the user from knowing whether the energy transmission has affected the targeted tissue until the tissue visible around the opaque tip has been affected. The likelihood of destroying healthy cells is greatly increased when such delayed and indirect feedback is used. Even with conventional devices having visually transparent probes, the accuracy is reduced by the inability to accurately identify and isolate the tissue to be ablated. For example, when electrodes on a conventional device are placed adjacent diseased tissue, there are no visual indicators accurately ensuring the device has been properly positioned and there are not safeguards to ensure healthy tissue next to the diseased tissue and underlying muscular tissue will not be adversely affected. The inability to accurately identify and isolate the tissue to be ablated can result in insufficient ablation. Thus, even when the probe is properly positioned, when too much energy is transferred to or from the device, ablation of healthy adjacent cells and/or underlying muscular cells can occur. On the other hand, when too little energy is transferred from the device, less than all of the targeted tissue is ablated.
The conventional approaches for treating Barrett's esophagus or other diseases requiring the precise ablation of relatively large areas of intralumenal tissue are insufficient in these regards. Thus, there is a need for an ablation device and method for using such a device that allow accurate and minimally invasive ablation of relatively large amounts of intralumenal patient tissue.